The present invention relates to a method and an apparatus for supporting high speed joining or searching in a relational data base (RDB) machine which executes an RDB operation in synchronism with the data transfer in a file system such as an RDB system.
In the data base (DB) machine which is synchronous with the data transfer, it is easy to carry out an operation relating to a single table, but in the join operation, data in one table must be stored into the DB machine, and if the join operation is performed in the DB machine, data to be transferred to a CPU increase. However, the join operation includes a large amount of processing and a need for rapid processing is high.
This is described in "Content Addressable File Store" by R. W. Michell, Proceedings of Online Conference on Database Technology, April 1976.
The CAFS (content addressable file store) supports high speed joining by utilizing a Hashed bit array or Hashing. However, when the Hash is used, a problem of synonym arises. It is therefore necessary to select the Hashing function which generates few synonyms. This is practically difficult because a selection of the function is dependent on a distribution of data.
In data base processing or file processing, searching is a basic operation. Since the searching is done very frequently and a processing load thereof is relatively high, it is important to improve the speed of the searching. If the searching is done by software, the efficiency of processing such as data comparison and data structure operation is lower than that attained by specialized hardware, and the efficiency is low in a general purpose computer.
As the LSI technology advances, an LSI chip can be manufactured with a relatively low cost and it has been proposed to develop specialized hardware for searching only so that the searching is speeded up by the hardware. See "Pipeline Searching and Sorting Modules as Components of a Dataflow Computer", Tanaka Y. et. al., IFIP Congress 80' pages 427-432, October 1980; and "Content Addressable Parallel Processors", Foster C. C., Van Nostrand Reinhold, 1976.
This is also described in the Japanese Patent Application No. 59-173310.